The present invention relates generally to control design methodology and, more particularly, to a method for automatic synthesis of multi-variable controllers.
The design and manufacture of new products has become an increasingly complex activity due to reliance on features requiring high performance controllers. In order to design controllers for a dynamic system, a designer must go through a number of operations in a design cycle.
First, a desired performance of the dynamic system is identified and qualified. Then, the designer must create a model characterizing the system. In the process of constructing the model, the designer may rely on prior knowledge encompassing available scientific formulas and on experimental data gathered from previous experiments conducted on the system. The model obtained is a mathematical representation of the system""s behavior.
Next, using the model previously created, a controller is designed for the system and the control design is tested to determine the performance of the controlled system. Depending upon the outcome of the tests, several portions of the design may be repeated, until the design results in a final product to be used with the system.
In the control design portion of the design cycle, standard design tools and methodologies are often used to design the controller. However, many systems and manufacturing processes have become too complex for such standard tools and methodologies, and the control design performed by such methodologies is often inadequate.
Existing control design tools and methodologies are created for control designers and require a high level of expertise. One shortcoming of such control design tools and methodologies is the selection of design parameters used in the design process. The design parameters must be selected manually by a knowledgeable designer, which often proves to be a difficult task. A typical example of such a tool is MATLAB(copyright) Control System Toolbox, available from Mathworks, Inc. of Natick, Mass.
Other known control design tools and methods attempt to solve the control design problem numerically by applying automatic optimization techniques to the entire set of design parameters in order to find optimal parameter values. For a large number of parameters, the optimization procedure is computationally intractable. One example of such software tool is QDES, described in detail in Linear Controller Design: Limits of Performance, by Boyd and Barratt, Prentice Hall 1991.
A method is disclosed for automatic synthesis of multi-variable controllers. A design sequence for designing a controller for a system is selected, wherein the controller includes one or more controller components. A first set of parameters associated to the one or more controller components is then selected. A second set of parameters associated to the first set of parameters is subsequently selected. One or more parameters of the second set are then iteratively modified to obtain a set of modified parameters, until a plurality of performance characteristics calculated using the second set of parameters meets a performance objective for the system.